JP2017080569A - Balancer device used for installing artificial knee joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balancer device which applies a load closer to a predetermined load to a knee joint part.SOLUTION: A balancer device (1) comprises a tibia fitting part (2), a femur fitting part (4), and a movement mechanism (6) for moving the femur fitting part relative to the tibia fitting part in a direction perpendicular to a proximal end surface of a tibia. The movement mechanism (6) comprises a fixed part (8) fitted to the tibia fitting part, a movable part (10) fitted to the femur fitting part and the fixed part, and a lock mechanism (22) for locking the movable part to the fixed part by a mechanically determined increment. The movable part can extend and contract to move the femur fitting part relative to the tibia fitting part. The movable part has an upper body portion (28) and a turning portion (30) rotatably fitted to the upper body portion and fixed to the femur fitting part. The balancer device also comprises a scale (34c) representing the angular position of the turning portion relative to the upper body portion.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a balancer device used between a femur and a tibia to install an artificial knee joint.

  Artificial knee joints are sometimes used to treat patients who have osteoarthritis or chronic rheumatism due to wear of the knee cartilage. FIG. 9 is a schematic side cross-sectional view showing the left leg femur and tibia with an artificial knee joint installed. As shown in FIG. 9, the artificial knee joint 100 includes a femur F so as to cover the tibial tray 102 and the surface liner 104 fixed to the proximal end Te of the tibia T and the distal end Fe of the femur F. And a femoral component 106 secured to the body. In some cases, a spacer (not shown) is inserted between the tibial tray 102 and the tibia T. The femur F and the tibia T are connected and pulled together mainly by ligaments (not shown) arranged on the left and right sides thereof, so that the femoral component 106 is pressed against the surface liner 104. ing. In the knee prosthesis 100, the femoral component 106 slides along the surface liner 104 when the knee is moved between a bent position (flexion position) and an extended position (extension position).

  FIG. 10 is a schematic side view showing the left leg tibia and femur partially excised for placement of the knee prosthesis. As shown in FIG. 10, the proximal end Te of the tibia T has an installation surface for removing the worn cartilage and fixing the tibial tray 102 to the tibia T, that is, the proximal end surface Tc. It has been excised (bone cut) to form. Similarly, the distal end Fe of the femur F is used to remove worn cartilage and to form five mounting surfaces Fc1-Fc5 for securing the femoral component 106 to the femur F. Has been excised (bone cut). The five installation surfaces include a distal end surface Fc1, a front installation surface Fc2 and a rear installation surface Fc3 perpendicular to the distal end surface Fc1, and a distal end surface Fc1, the front installation surface Fc2, and the rear installation surface Fc3. Two inclined installation surfaces Fc4 and Fc5.

  The proximal end surface Tc of the tibia T and the distal end surface Fc1 of the femur F are respectively connected to the proximal end of the tibia T and the distal end of the femur F so that the patient's height does not change after the artificial knee joint 100 is attached. They are formed at predetermined distances LT and LF from the end. Generally, the proximal end surface Tc of the tibia T is formed perpendicular to the axis of the tibia T. After forming the proximal end face Tc of the tibia T and the distal end face Fc1 of the femur F, the tension state of the ligament (the ligament tension and the left / right balance) when the knee is in the extended position is adjusted. Since the proximal end face Tc of the patient's tibia T and the distal end face Fc1 of the femur F before adjustment are not parallel due to the unbalance of the left and right ligaments, by releasing a part of the soft tissue of the ligament, The proximal end face Tc and the distal end face Fc1 are made parallel. At this time, for example, a balancer device is inserted between the tibia T and the femur F to obtain a predetermined tension state of the ligament. Next, after the knee is bent and the tension of the ligament is confirmed, the positions of the anterior placement surface Fc2 and the posterior placement surface Fc3 of the femur are determined (see, for example, Patent Document 1).

  Japanese people often bend their knee joints deeper than their Western counterparts. Therefore, by making the tension state of the ligament when the knee is in the flexed position match the tension state of the ligament when the knee is in the extended position, it is possible to reduce discomfort and wear after installing the artificial knee joint Particularly desired. The balancer device described in Patent Document 1 can substantially match the tension state of the ligament when the knee is in the bent position with the tension state of the ligament when the knee is in the extended position. Increases the effectiveness of the installation technique.

JP 2013-230 A JP 2008-183083 A

  In the balancer device described in Patent Document 1, when adjusting the tension state of the ligament, the femur is gradually moved away from the tibia using a torque driver, and a predetermined load is applied from the outside of the balancer device. On the other hand, the locking position of the femur with respect to the tibia is determined by engaging claw levers with a number of hooks provided around the rotating body. Adjustment will be made at incremental positions determined mechanically. Therefore, the load adjusted at the incremental position may slightly deviate from the predetermined load. As a result, the predetermined load may not be accurately transmitted to the knee joint. Further, when changing the tension state of the ligament, for example, by cutting a part of the ligament, it may require skill to accurately realize the predetermined load at the incremental position.

  Also, in the balancer device described in Patent Document 1, the parts that support the femur when the knee is in the extended position are different from the parts that support the femur when the knee is in the bent position, so the parts are replaced. There is a need to. At this time, if the position when the balancer device is reinstalled is shifted, the tension state measured when the knee is in the extended position may not match the tension state measured when the knee is in the bent position. As a result, femoral osteotomy may not be accurate when the knee is in a flexed position.

  Therefore, a first object of the present invention is to provide a balancer device capable of applying a load closer to a predetermined load to the knee joint.

  The second object of the present invention is to provide a balancer device that can more easily match the tension measured when the knee is in the extended position and the tension measured when the knee is in the bent position. There is.

  In order to achieve the first object, a balancer device according to the present invention used between a femur and a tibia to install an artificial knee joint includes a tibial attachment portion attached to a proximal end surface of the tibia, A femoral attachment for supporting the distal end of the bone; and a movement mechanism for moving the femoral attachment relative to the tibial attachment in a direction perpendicular to the proximal end surface of the tibia, the movement mechanism comprising: A fixed part attached to the tibial attachment part, a movable part attached to the femoral attachment part and the fixed part so that the femoral attachment part can be moved relative to the tibial attachment part, and the movable part mechanically with respect to the fixed part It has a locking mechanism that locks at a predetermined increment position, and the movable part can be expanded and contracted in the vertical direction and is biased in the extending direction, and the extending direction of the movable part pulls the femoral attachment part from the tibial attachment part. It is characterized by the direction of separation That.

  In the balancer device configured as described above, when adjusting the tension state of the ligament, the femoral attachment portion is gradually moved away from the tibial attachment portion by moving the movable portion upward with respect to the fixed portion. The movable part is locked against the force caused by ligament tension by a locking mechanism that locks in a mechanically determined incremental position relative to the fixed part. On the other hand, since the movable part can be expanded and contracted in the vertical direction and is urged in the extending direction, the femoral attachment part is always pressed against the distal end of the femur with a load balanced with the ligament tension. It is in. Therefore, it becomes possible to adjust in the tension state of the ligament which is not restrained by the incremental position determined mechanically, and a load closer to a predetermined load can be applied to the knee joint.

  Further, when changing the tension state of the ligament by cutting a part of the ligament or the like, the movable part expands and contracts in the vertical direction to follow the change in the tension state of the ligament, so the predetermined load at the incremental position It becomes easy to realize accurately.

  In an embodiment of the balancer device according to the present invention, preferably, the fixed part has a vertical hole, and the movable part moves in the vertical direction with respect to the slide rack part fitted in the vertical hole and the slide rack part. A possible upper body portion and a spring that biases the upper body portion upwardly relative to the slide rack portion;

  In the embodiment of the balancer device according to the present invention, preferably, the balancer apparatus further includes a scale representing the vertical position of the movable part relative to the fixed part and a scale representing the load by which the movable part is pushed upward relative to the fixed part. In an embodiment of the balancer device according to the present invention, it is more preferable that the balancer device has a rotating portion that is rotatably attached to the upper body portion, and the rotating portion is fixed to the femoral attachment portion and is rotated relative to the upper body portion. It has a scale representing the angular position of the part.

  Since the balancer device configured as described above has a scale representing the load by which the movable part is pushed upward, it is further easy to accurately realize the predetermined load at the increment position.

  In order to achieve the second object, in the embodiment of the balancer device according to the present invention, preferably, the femoral attachment portion has an upper surface, and the spacer is attached to the upper surface when the knee is in the extended position. A sizing block body is attached to the top surface when the knee is in a refractive position, and more preferably, during a bearing trial, a trial component is attached to the top surface.

  In the balancer device configured as described above, the femur is supported by the same femoral attachment portion even when the knee is in the extended position or the bent position. Therefore, the tension state measured when the knee is in the extended position and the tension state measured when the knee is in the bent position can be more easily matched.

  The balancer device according to the present invention can apply a load closer to a predetermined load to the knee joint.

  In addition, the balancer device according to the present invention can more easily match the tension state measured when the knee is in the extended position and the tension state measured when the knee is in the bent position.

1 is a perspective view of a balancer device according to the present invention used when a knee is in an extended position. FIG. It is a disassembled perspective view of the balancer apparatus of FIG. It is a longitudinal cross-sectional view of the balancer apparatus of FIG. FIG. 2 is a cutaway perspective view of the balancer device of FIG. 1. It is a front view of the balancer apparatus of FIG. 1 is a perspective view of a balancer device according to the present invention used when a knee is in a bent position. FIG. It is a disassembled perspective view of the balancer apparatus of FIG. It is a perspective view of the balancer device by the present invention used for a trial. It is a schematic side sectional view showing a femur and a tibia in which an artificial knee joint is installed. FIG. 6 is a schematic side view showing a tibia and a femur partially excised for placement of an artificial knee joint.

  Hereinafter, an embodiment of a balancer device according to the present invention used between a femur and a tibia to install an artificial knee joint will be described with reference to the drawings. The balancer device according to the invention is used with the tibia as a reference. Hereinafter, the direction in which the tibia extends is referred to as the up-down direction A, and the left-right direction and the front-back direction of the patient in the tibia are referred to as the left-right direction B and the front-back direction C, respectively (see FIG. 1). The terms “distal” and “proximal” are also used for the patient's torso. Moreover, in embodiment described below, a left leg is illustrated. Thus, the terms “inside” and “outside” correspond to the right and left sides of the left leg, respectively.

  First, the balancer device 1 according to the present invention used when the knee is in the extended position will be described with reference to FIGS. In the extended position, the balancer device 1 is used together with the spacer 12 (see FIG. 1).

  As shown in FIG. 1, the balancer device 1 includes a tibial attachment portion 2 attached to the proximal end surface Tc of the tibia T and a femoral attachment portion 4 that supports a distal end portion (distal end surface Fc1) of the femur F. And a moving mechanism 6 that moves the femoral attachment part 4 in a direction (vertical direction) A perpendicular to the proximal end surface Tc of the tibia T with respect to the tibial attachment part 2. The moving mechanism 6 has a fixed part 8 to which the tibial attachment part 2 is attached, and a movable part 10 to be attached to the femoral attachment part 4 and the fixed part 8 so that the femoral attachment part 4 can move relative to the tibial attachment part 2. doing.

  As shown in FIG. 2, the tibial attachment portion 2 includes a positioning portion 2a positioned on the proximal end surface Tc of the tibia T, a support arm 2b extending forward from the positioning portion 2a, and a support portion 2b. And a coupling portion 2c for attaching to the housing. The positioning portion 2a is plate-shaped and has a lower surface 2d that rests on the proximal end surface Tc of the tibia T. The support arm 2b is preferably arranged to be shifted leftward or rightward from the center of the tibia T when the tibial attachment 2 is positioned on the proximal end surface Tc of the tibia T. The coupling portion 2c is fitted to one of the T-shaped protrusions 14 provided on both sides in the left-right direction B of the fixing portion 8 (specifically, a lower main body portion 18 described later) and is slidably inserted from below. It has a contact surface 2e that can contact the protrusion 14 after insertion. The tibial attachment portion 2 is fixed to the fixing portion 8 (lower main body portion 18) with a bolt 2f (see FIG. 5) via the coupling portion 2c and the protrusion 14.

  The femur attachment portion 4 is an attachment portion 4a disposed between the femur F and the tibial attachment portion 2, a support arm 4b extending forward from the attachment portion 4a, and a support arm 4b for attaching the support arm 4b to the movable portion 10. The coupling portion 4c is provided. The attachment portion 4a has a plate shape and has an upper surface 4d to which a spacer 12 (see FIG. 1) and the like are attached. The support arm 4b is preferably arranged to be shifted to the left or right from the center of the femur F when the femur attachment portion 4 is positioned between the femur F and the tibial attachment portion 2. It is preferable that the shifted direction is the same as the direction in which the support arm 2b of the tibial attachment portion 2 is shifted. The coupling portion 4c is fitted to one of the T-shaped projections 16 (only one of which is shown in FIG. 2) provided on both sides in the left-right direction B of the movable portion 10 (specifically, a rotating portion 30 described later). And has a contact surface 4e that can be slidably inserted from above and that contacts the protrusion 16 after insertion. The femur attachment portion 4 is fixed to the movable portion 10 (the rotating portion 30) by a bolt 4f (see FIG. 5) via the coupling portion 4c and the protrusion 16.

  As shown in FIGS. 2 to 4, the fixed portion 8 of the moving mechanism 6 rotates in a vertically long lower main body portion 18 and a left and right direction hole 18 a provided in a lower portion of the lower main body portion 18 so as to extend in the left and right direction B. The rotating body 20 is supported in a possible manner. The lower main body portion 18 has a vertical hole 18b that penetrates a slide rack portion 26 of the movable portion 10 described later so as to be movable in the vertical direction A, and a vertical direction in which a scale plate 34 described later is slidably received. A groove 18c is provided. The rotating body 20 has a pinion 20 a that is operatively engaged with the slide rack portion 26. In order to engage the slide rack portion 26 and the pinion 20a, the left-right direction hole 18a and the up-down direction hole 18b communicate with each other. The tip of the rotating body 20 has a convex portion 20b or a concave portion into which a tool (for example, a T wrench) for rotating the rotating body 20 is fitted. By rotating the pinion 20 a of the rotating body 20, the slide rack portion 26 of the movable portion 10 is moved in the vertical direction A with respect to the fixed portion 8, that is, the femoral attachment portion 4 is moved vertically with respect to the tibial attachment portion 2. Allows movement in direction A.

  The moving mechanism 6 further has a locking mechanism 22 that locks the movable part 10 with respect to the fixed part 8 in mechanically determined increments, so that the femoral attachment part 4 is relative to the tibial attachment part 2. To prevent it from descending. Specifically, the lock mechanism 22 includes a claw lever 22b that can be engaged with a large number of hooks 22a provided around the rotating body 20, and a shaft 22c that pivotally supports the claw lever 22b. The spring 22d urges the claw lever 22b toward the catching portion 22a so as to prevent the movable portion 10 from descending (that is, to keep the movable portion 10 in a lifted state). ing.

  As shown in FIG. 2, the fixing portion 8 of the moving mechanism 6 further includes an auxiliary support portion 24 that contacts the tibia T (actually, the skin on the tibia) below the tibial attachment portion 2. Preferably it is. Specifically, the auxiliary support portion 24 includes a guide protrusion 24a provided on the lower main body portion 18 so as to be inclined obliquely downward toward the tibia T, and an extension element 24b extending from the guide protrusion 24a toward the tibia T. The extension element 24b is constituted by a knob 24c for fixing the extension element 24b to the fixing portion 8 (specifically, the lower main body portion 18). The extension element 24b is slidable along the guide protrusion 24a, and is fixed to the fixing portion 8 (lower main body portion 18) in a state of being in contact with the skin on the tibia T.

  As shown in FIGS. 2 to 4, the movable portion 10 of the moving mechanism 6 includes a cylindrical slide rack portion 26 that fits in the vertical hole 18 b of the lower main body portion 18 of the fixed portion 8, and a slide rack portion 26. On the other hand, the upper main body portion 28 movable in the vertical direction A, the rotating portion 30 rotatably attached to the upper portion 28e of the upper main body portion 28, and the upper main body portion 28 are attached to the slide rack portion 26 upward. A spring 32 is provided.

  As shown in FIGS. 3 and 4, the slide rack portion 26 has a vertical through hole 26a and a rack portion 26b that engages with the pinion 20a, and has a through hole 26d below the vertical through hole 26a. A bottom lid 26c is provided.

  The upper body portion 28 has a first portion 28a that fits in the vertical hole 18b of the lower body portion 18, and a second portion that extends downward from the first portion 28a and has an outer diameter smaller than that of the first portion 28a. Part 28b, a stopper 28d attached to the lower end of the second part 28b and having an outer diameter larger than that of the second part 28b, and an upper part 28e provided on the first part 28a. Yes. In the present embodiment, the vertical hole 18b of the lower main body portion 18 has a relatively small diameter upper portion into which the first portion 28a of the upper main body portion 28 is fitted, and a relatively large diameter into which the slide rack portion 26 is fitted. It has a lower part. The second portion 28b is fitted in the through hole 26d of the bottom lid 26c. The spring 32 is disposed between the stepped portion between the first portion 28a and the second portion 28b and the bottom lid 28d and abuts against them. Thus, the movable part 10 can be expanded and contracted in the vertical direction A and is biased in the extending direction, and the direction in which the movable part 10 extends is the direction in which the femoral attachment part 4 is pulled away from the tibial attachment part 2.

  As shown in FIGS. 2 to 4, the rotating portion 30 includes a shaft portion 30 a that is rotatably inserted into a circular front-rear hole 28 f provided in the upper portion 28 e of the upper main body portion 28, and a shaft portion 30 a. It has a joint portion 30b extending rearward and coupled to the femoral attachment portion 4, and a needle portion 30c removably attached to a portion of the shaft portion 30a protruding forward from the front / rear hole 28f. The upper surface 28g of the upper portion 28e is formed in an arc shape centering on the axis 28h of the front-rear direction hole 28f, and the rotating portion 30b preferably has a contact surface 30d that slidably contacts the upper surface 28g.

  As shown in FIGS. 2 to 5, the upper body portion 28 also has a scale plate 34 slidably disposed in the vertical groove 18 c of the lower body portion 18. The scale plate 34 is attached to the upper part 28e of the upper main body portion 28, and has a lower scale 34a, an intermediate scale 34b, and an upper scale 34c. The lower scale 34a and the intermediate scale 34b can be seen through a window 18d provided in the lower main body portion 18 along the groove 18c.

  The lower scale 34a is a scale representing a load that the movable part 10 is pushed upward with respect to the fixed part 8, that is, an upward load that acts on the femoral attachment part 4 with respect to the tibial attachment part 2. This is indicated by an instruction line 26e (see FIGS. 2 and 5; in this embodiment, a step) provided in the portion 26. The indicator line 26e is visible through windows 18e, 34d provided on the lower body portion 18 and the scale plate 34 and aligned with each other.

  The intermediate scale 34b is a scale representing the vertical position of the movable part 10 relative to the fixed part 8, that is, the vertical position of the femoral attachment part 4 relative to the tibial attachment part 2, and an indicator line 18f provided at the edge of the window 18d. (Refer to FIG. 2 and FIG. 5.

  The upper scale 34c is a scale that represents the angular position of the rotating portion 30 with respect to the upper body portion 28, that is, the angular position of the femoral attachment portion 4 with respect to the tibial attachment portion 2, and is indicated by the needle portion 30c. When the lower surface 2d of the tibial attachment portion 2 and the upper surface 12b of the spacer 12 described later are parallel (see FIG. 3), that is, when the proximal end surface Tc of the tibia T and the distal end surface Fc1 of the femur F are parallel. The needle portion 30c indicates zero.

  As shown in FIGS. 1 and 3, the spacer 12 has a lower surface 12a that is placed on the upper surface 4d of the femoral attachment portion 4 and an upper surface 12b that is parallel to the lower surface 12a. The lower surface 12 a has two protrusions 12 c that can be fitted into two holes 4 f (see FIG. 4) provided on the upper surface 4 d of the femur attachment portion 4.

  Next, with reference to FIG.6 and FIG.7, the balancer apparatus 1 used in the state which made the knee into the bending position is demonstrated. In the bent position, the balancer device 1 is used together with the sizing unit 36.

  As shown in FIGS. 6 and 7, a sizing block unit 36 is attached to the balancer device 1 instead of the spacer 12 shown in FIGS. 1 and 3. Specifically, the sizing block unit 36 includes a sizing block tower 38 and a sizing block main body 40.

  The sizing block tower 38 has a tower main body 38a extending in the vertical direction and having a non-circular cross section, and a mounting protrusion 38b protruding downward from the tower main body 38a. The sizing block tower 38 can pass through a hole 4g provided in front of the attachment portion 4a of the femoral attachment portion 4. The mounting protrusion 38b of the sizing block tower 38 penetrating through the hole 4g can be fitted into the hole 2f provided in the positioning portion 2a of the tibial mounting portion 2, so that the sizing block tower 38 is separated from the tibial mounting portion 2. Extends upward.

  The sizing block main body 40 includes a vertical hole 40a that is slidably fitted to the tower main body 38a, a lower surface 40b that is in contact with the upper surface 4d of the femoral attachment portion 4, and an installation reference hole for an osteotomy jig (not shown). Through the distal end surface Fc1 of the femur F, and the femoral F with the installation surface Fc2 for mounting the femoral component 106 (see FIG. 9) on the femur F. The guide groove 40d is provided. Therefore, when the movable part 10 is moved in the vertical direction A with respect to the fixed part 8, the femoral attachment part 4 moves in the vertical direction A with respect to the tibial attachment part 2, and the sizing block main body 40 moves to the sizing block tower 38. On the other hand, it moves in the vertical direction A.

  Next, the balancer apparatus 1 used for the bearing trial will be described with reference to FIG. The bearing trial is performed by attaching a femoral component trial 106 ′, which is a test femoral component having the same shape as the femoral component 106 attached to the femur F, to the femur F and confirming the tension state of the ligament. is there. In the bearing trial, the balancer device 1 is used together with the trial spacer 42.

  As shown in FIG. 8, a trial spacer 42 is attached to the balancer device 1 instead of the spacer 12 shown in FIGS. 1 and 3. The trial spacer 42 has a lower surface 42a that is placed on the upper surface 4d of the femoral attachment 4 and an upper surface 42b that slidably supports the femoral component trial 106 '. The lower surface 42 a has two protrusions (not shown) that can be fitted into two holes 4 f (see FIGS. 2 and 4) provided in the upper surface 4 d of the femoral attachment portion 4.

  Each component of the balancer apparatus 1, the spacer 12, the sizing block unit 36, and the trial spacer 42 may be made of a material that enables sterilization by a sterilization apparatus (autoclave). Such a material is, for example, a stainless steel material.

  Next, the operation of the balancer device according to the present invention will be described.

  The balancer device 1 with the spacer 12 attached is placed between the tibia T and the femur F with the patient's knee in the extended position. Specifically, the tibial attachment portion 2 is attached to the proximal end face Tc of the tibia T. Further, in a state where the positioning portion 2a of the tibial attachment portion 2 is pressed against the proximal end surface Tc of the tibia T, the extension element 24b of the auxiliary support portion 24 is moved along the guide protrusion 24a to contact the tibia T. The extension element 24b is fixed to the lower body portion 18 by a knob 24c. Accordingly, the balancer device 1 is prevented from being tilted and attached by the weight of the moving mechanism 6 or the like so that the positioning portion 2a of the tibial attachment portion 2 is separated from the proximal end surface Tc of the tibia T. Since the support arm 2b of the tibial attachment portion 2 and the support arm 4b of the femur attachment portion 4 are arranged shifted to the right (or left) of the tibia T, the balancer device 1 does not interfere with the patella ligament. To be operated.

  The T handle or the like is engaged with the convex portion 20b of the rotating body 20 and rotated to rotate the pinion 20a, lift the movable portion 10 via the slide rack portion 26, and move the femoral attachment portion 4 to the femur F. The distal end face Fc1 is brought into contact and further lifted. The lock mechanism 22 prevents the rotating body 22 from rotating in the direction in which the femoral attachment portion 4 is lowered, and maintains the femoral attachment portion 4 in a lifted state.

  In order to adjust the tension state of the ligament, the femoral attachment part 4 is gradually moved away from the tibial attachment part 2 by moving the movable part 10 upward with respect to the fixed part 8. As described above, the movable portion 10 is locked against the force generated by the ligament tension by the lock mechanism 22 that locks the fixed portion 8 at a mechanically determined incremental position. On the other hand, since the movable part 10 can be expanded and contracted in the vertical direction A and is urged in the extending direction, the femoral attachment part 4 and the spacer 12 have a distal end face Fc1 of the femur F with a load balanced with the tension of the ligament. It is in a state where it is always pressed. Therefore, the ligament can be adjusted in a ligament tension state that is not constrained to a mechanically determined incremental position, and a load closer to a predetermined load can be applied to the knee joint.

  The load acting between the distal end face Fc1 of the femur F and the proximal end face Tc of the tibia T is determined by the amount of contraction of the spring 32 and can be read by the lower scale 34a. The ligament is adjusted such that the ligament tension state (tension and left / right balance) between the femur F and the tibia T becomes a predetermined load. When changing the tension state of the ligament, for example, by cutting a part of the ligament, the movable portion 10 expands and contracts in the vertical direction A to follow the change in the tension state of the ligament. Further, the change in the load is reflected on the lower scale 34a. As a result, it is easy to accurately realize the predetermined load at the incremental position. The interval between the femur F and the tibia T is referred to the vertical scale 34b, and the left and right balance of the ligament is referred to the angular scale 34c.

  When the adjustment of the ligament in the extended position is completed, the spacer 12 is removed from the balancer device 1 and the sizing block unit 36 is attached to the balancer device 1 in order to adjust the ligament in the bent position. At this time, the femur F is supported by the same femoral attachment portion 4 when the knee is in the extended position and in the bent position, and it is preferable that the balancer device 1 is not required to be removed from the patient. Therefore, the tension state measured when the knee is in the extended position and the tension state measured when the knee is in the bent position can be more easily matched.

  When the adjustment of the ligament in the bent position is completed, the sizing block unit 36 is removed from the balancer device 1 and the trial spacer 42 is attached to the balancer device 1 in order to perform a bearing trial. At this time, the femur F is supported by the same femoral attachment part 4 when the knee is in the extended position or the bent position and when performing the bearing trial, and it is preferable that the balancer device 1 is not required to be removed from the patient. Therefore, the bearing trial is performed in substantially the same state as the tension state measured when the knee is in the extended position and the tension state measured when the knee is in the bent position.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims. Needless to say, these are also included within the scope of the present invention.

  In the above embodiment, the first portion 28 a of the upper body portion 28 is fitted to the upper portion of the vertical hole 18 b of the lower body portion 18, but the vertical through hole of the slide rack portion 26. 26a may be configured to fit.

DESCRIPTION OF SYMBOLS 1 Balancer apparatus 2 Tibial attachment part 4 Femur attachment part 4d Upper surface 6 Movement mechanism 8 Fixed part 10 Movable part 18b Vertical direction hole 22 Lock mechanism 26 Slide rack part 28 Upper main body part 30 Turning part 32 Spring 34a Lower scale 34b Intermediate scale 34c Upper scale A Vertical direction F Femur Fc1 Distal end face T Tibia Tc Proximal end face

Claims (5)

A balancer device used between a femur and a tibia to install a knee prosthesis, the tibial attachment being attached to a proximal end surface of the tibia;
A femoral attachment that supports the distal end of the femur;
A moving mechanism for moving the femoral attachment portion in the vertical direction perpendicular to the proximal end surface of the tibia with respect to the tibial attachment portion,
The moving mechanism includes a fixed portion attached to the tibial attachment portion, a movable portion attached to the femoral attachment portion and the fixed portion so that the femoral attachment portion can be moved relative to the tibial attachment portion, and the movable portion A locking mechanism for locking the portion with respect to the fixed portion at a mechanically determined incremental position;
The movable part is extendable in the vertical direction to move the femoral attachment part relative to the tibial attachment part,
The movable part further has an upper body part and a turning part rotatably attached to the upper body part, and the turning part is fixed to the femoral attachment part,
The balancer device further includes a scale indicating an angular position of the rotating portion with respect to the upper main body portion. The fixing portion has a vertical hole,
The movable portion includes a slide rack portion that fits into the vertical hole, the upper main body portion that is movable in the vertical direction with respect to the slide rack portion, and the upper main body portion that is located above the slide rack portion. The balancer device according to claim 1, further comprising a spring that biases the spring.   The balancer device according to claim 1, further comprising a scale representing a vertical position of the movable part with respect to the fixed part, and a scale representing a load with which the movable part is pushed upward with respect to the fixed part. . The femoral attachment has an upper surface;
When the knee is in the extended position, a spacer is attached to the upper surface,
The balancer device according to claim 1, wherein a sizing block body is attached to the upper surface when the knee is in a refractive position.   The balancer device of claim 4, wherein a trial component is attached to the top surface during a bearing trial.

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